30
Tire pressure that is too low for your weight and the riding
conditions can cause a puncture of the tube by allowing the tire
to deform sufficiently to pinch the inner tube between the rim and
the riding surface.
CAUTION: Pencil type automotive tire gauges can be inaccurate and should
not be relied upon for consistent, accurate pressure readings. Instead, use a
high quality dial gauge.
Ask your dealer to recommend the best tire pressure for the
kind of riding you will most often do, and have the dealer inflate
your tires to that pressure. Then, check inflation as described in
Section 1.C so you’ll know how correctly inflated tires should
look and feel. Some tires may need to be brought up to
pressure every week or two.
Some special high-performance tires have unidirectional
treads: their tread pattern is designed to work better in one
direction than in the other. The sidewall marking of a
unidirectional tire will have an arrow showing the correct
rotation direction. If your bike has unidirectional tires, be sure
that they are mounted to rotate in the correct direction.
2. Tire Valves
There are primarily two kinds of bicycle tube valves: The
Schraeder Valve and the Presta Valve. The bicycle pump you use
must have the fitting appropriate to the valve stems on your
bicycle.
The Schraeder valve (fig. 23) is like the
valve on a car tire. To inflate a Schraeder
valve tube, remove the valve cap and clamp
the pump fitting onto the end of the valve
stem. To let air out of a Schraeder valve,
depress the pin in the end of the valve stem
with the end of a key or other appropriate
object.
The Presta valve (fig. 24) has a narrower diameter and is only
found on bicycle tires. To inflate a Presta valve tube using a Presta
headed bicycle pump, remove the valve cap; unscrew (counter-
clockwise) the valve stem lock nut; and push
down on the valve stem to free it up. Then push
the pump head on to the valve head and
inflate. To inflate a Presta valve with a
Schraeder pump fitting, you’ll need a Presta
adapter (available at your bike shop) which
screws on to the valve stem once you’ve freed
up the valve. The adapter fits into the
Schraeder pump fitting. Close the valve after
invlation. To let air out of a Presta valve, open
up the valve stem lock nut and depress the
valve stem.
WARNING: Patching a tube is an emergency repair. Ifyou do not apply the
patch correctly or apply several patches, the tube can fail, resulting in pos-
sible tube failure, which could cause you to loose control and fall. Replace a
patched tube as soon as possible.
!
!
Fig. 24
Fig. 23
